Light-emitting devices capable of realizing high-luminance white light, such as red, green, and blue light-emitting diodes (LEDs), have been developed based on the development of molecular beam epitaxial growth and metal organic chemical vapor deposition of gallium nitride (GaN), and the like.
Such LEDs have excellent environmental friendliness because they include no environmentally harmful materials such as mercury (Hg), which has conventionally been used in lighting apparatuses such as, for example, incandescent lamps and fluorescent lamps, and also have other advantages, for example, a long lifespan and low power consumption. Therefore, existing light sources are being replaced with LEDs. The core competitive factor of the LEDs is realization of high luminance by high-efficiency and high-output chip and package technologies.
Such light-emitting devices need to have uniform illuminance and high reliability.